Lincoln Electric SVM194-A service manual Engine Idler Circuit, 11135 10657, 10658, 10911

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E-9	THEORY OF OPERATION						E-9
ENGINE IDLER CIRCUIT		Classic® 300D Perkins (Codes 10545, 10546,
Classic® 300G (Codes 10659, 10912, and
11135)		10657, 10658, 10911, and 10927)
The Zenith ECU used in the Classic® 300G con-		The above models use a high speed solenoid,
trols whether the engine operates at high idle or		connected to the governor linkage, and operated
low idle. Closing the circuit between pins #11 and		by the idler/engine protection PC board. In these
#13 of the ECU signal that high RPM is required		machines, the solenoid increases the RPM when
and the engine immediately accelerates to high		activated.
idle RPM. Opening this will cause the engine		When the idle switch is in the auto position, and
RPM to drop to low idle speed, (about 1360 RPM)
after a delay of about 15 seconds. If the pin #11		welding current is being drawn, the reed switch
to pin #13 circuit is re-closed during this delay,		CR2 is closed. This signals the idler PC board to
engine RPM will remain high.		activate the high speed solenoid, which then
		increases the engine speed to high idle RPM.
The current sensor PC board detects current flow		When auxiliary power is being used, the current is
in both the auxiliary and the weld circuits. When		passed through the toroidal current transformer.
sufficient current is flowing in either of these cir-		This also signals the idler PC board to activate the
cuits, the current sensor PC board closes the #11		high speed solenoid. When welding ceases or
- #13 circuit, when current flow ceases, the circuit		the auxiliary load is removed, a preset time delay
is opened.		of about 15 seconds starts. When this 15 second
		delay has passed, the idler PC board deactivates
The idle switch and the current sensing PC board		the high speed solenoid, and allows the machine
are wired in parallel across the #11 - #13 circuit		will return to a low speed condition. If welding is
described above.	When the idle switch is set to	resumed, or an auxiliary load is applied during this
the high position, the contacts are closed and the		delay, the solenoid will remain active and the
ECU operates the engine continuously at high		engine RPM remains high.
RPM. When the idle switch is in the Auto position,		When the idle switch is in the high position, the
the contacts are open, and the current sensor PC
board has control of the #11 - #13 circuit.		reed switch CR2 is bypassed, signaling the PC
		board to activate the solenoid.
		Classic® 300D Perkins (Codes 11110, 11111,
		11248,	11249,	11280,	11281,	11411,	11412,
		11472, and 11473)

The above models use a two winding idle sole- noid, connected to the governor linkage, and operated by the idler/engine protection PC board. The engine normally runs at high RPM, and is controlled by the governor. When the idle switch is in the auto position and no weld or auxiliary loads are applied, the idler/engine protection PC board starts a 15 second delay. When this delay has passed, both the pull and hold coils of the solenoid are activated. After about 0.75 seconds, the pull coil is deactivated leaving the still active hold coil to maintain the low idle position of the solenoid.

NOTE: Unshaded areas of Block Logic

Diagram are the subject of discussion

CLASSIC® 300D & 300G